The issue was that a Macro Template
used on this code
// öäüß procedure TForm1.FormCreate(Sender: TObject); begin ShowMessage('TEST'); end;
while TEST was selected
generated code like this
// öäüß procedure TForm1.FormCreate(Sender: TObject); begin ShowMessage(''); (TEST) end;
The reason again was improper use of positions and offsets into the editor buffer in conjunction with some Unicode characters above the code. So the insert position was calculated by 4 bytes too high, hence the macro code was inserted 4 characters behind the start of the original selection.